U.S. patent application number 15/341854 was filed with the patent office on 2018-05-03 for surge-tolerant power supply system.
This patent application is currently assigned to ELECTRO-MOTIVE DIESEL, INC.. The applicant listed for this patent is ELECTRO-MOTIVE DIESEL, INC.. Invention is credited to James F. WIEMEYER.
Application Number | 20180123462 15/341854 |
Document ID | / |
Family ID | 62020577 |
Filed Date | 2018-05-03 |
United States Patent
Application |
20180123462 |
Kind Code |
A1 |
WIEMEYER; James F. |
May 3, 2018 |
SURGE-TOLERANT POWER SUPPLY SYSTEM
Abstract
An apparatus for providing surge-tolerant power to an appliance
is provided. The apparatus includes an input circuit for receiving
a source of DC voltage. The apparatus also includes a pass device
having a first terminal, a control terminal and a second terminal.
Further, the apparatus includes a first means for providing an
output voltage based on an input of the pass device. The apparatus
also includes a second means for applying a voltage to a control
terminal of the pass device based on the output voltage. The
voltage is sufficient to put the pass device into a low impedance
state between the first terminal and the second terminal
thereof.
Inventors: |
WIEMEYER; James F.; (Homer
Glen, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ELECTRO-MOTIVE DIESEL, INC. |
LaGrange |
IL |
US |
|
|
Assignee: |
ELECTRO-MOTIVE DIESEL, INC.
LaGrange
IL
|
Family ID: |
62020577 |
Appl. No.: |
15/341854 |
Filed: |
November 2, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M 1/14 20130101; H02M
1/36 20130101; H02M 3/335 20130101; H02M 3/33507 20130101; H02M
1/32 20130101 |
International
Class: |
H02M 3/335 20060101
H02M003/335; H02M 1/14 20060101 H02M001/14; H02M 1/36 20060101
H02M001/36; H02M 1/32 20060101 H02M001/32 |
Claims
1. A surge-tolerant power supply system comprising: an input
circuit having a first input terminal and a second input terminal
configured to receive a source of DC voltage; an N-channel MOSFET
having a gate terminal, a source terminal, and a drain terminal,
the N-channel MOSFET having a characteristic threshold voltage
between the gate terminal and the source terminal, and the drain
terminal being electrically connected to a positive output of the
input circuit; a switch mode DC-to-DC converter having an input
electrically connected to the source terminal of the N-channel
MOSFET and a negative output of the input circuit; a transformer
driver having an input electrically connected to an output of the
switch mode DC-to-DC converter; an isolation transformer having a
primary winding electrically connected to an output of the
transformer driver; a rectifier-filter circuit having an input
electrically connected to a secondary winding of the isolation
transformer and having an output configured to provide an output
voltage; a bias circuit having a first input electrically connected
to the positive output of the input circuit and a second input
electrically connected to the negative output of the input circuit;
and a DC bias boost circuit having a first input electrically
connected to an auxiliary winding of the isolation transformer, a
second input electrically connected to an output of the bias
circuit, and an output electrically connected to the gate terminal
of the N-channel MOSFET, wherein the DC bias boost circuit is
configured to apply a voltage at the gate terminal of the N-channel
MOSFET that exceeds the characteristic threshold voltage between
the gate terminal and the source terminal of the N-channel
MOSFET.
2. The surge-tolerant power supply system of claim 1, wherein the
bias circuit is configured to provide a voltage ramp at the output
of the bias circuit during a start-up period.
3. The surge-tolerant power supply system of claim 1, wherein the
input circuit comprises a transient voltage suppressor having a
first terminal electrically connected to the first input terminal
of the input circuit and a second terminal electrically connected
to the second input terminal of the input circuit.
4. The surge-tolerant power supply system of claim 1, wherein the
input circuit comprises a polarity protection circuit having a
first terminal electrically connected to the first input terminal
of the input circuit and a second terminal electrically connected
to the positive output of the input circuit.
5. The surge-tolerant power supply system of claim 1, wherein the
transformer driver is configured to delay an output signal of the
transformer driver for a predetermined time during a start-up
period.
6. The surge-tolerant power supply system of claim 1, wherein the
transformer driver comprises an over-voltage detection circuit
configured to shut down an output signal of the transformer driver
when a voltage level at the positive output of the input circuit is
above a predetermined level.
7. The surge-tolerant power supply system of claim 1, wherein the
transformer driver comprises a programmable processor configured to
shut down an output signal of the transformer driver when a voltage
level at the positive output of the input circuit is above a
predetermined level.
8. A surge-tolerant power supply comprising: an input circuit
configured to receive a source of DC voltage; a pass device having
a first terminal electrically connected to a positive output of the
input circuit; a voltage converter circuit having an input and at
least two isolated outputs, the input being electrically connected
to a second terminal of the pass device, and a first isolated
output of the at least two isolated outputs is configured to
provide an output voltage; and a bias circuit having a first input
electrically connected to a second output of the at least two
isolated outputs of the voltage converter circuit, a second input
electrically connected to the positive output of the input circuit,
and an output electrically connected to a control terminal of the
pass device, wherein the bias circuit is configured to apply a
voltage on the control terminal of the pass device sufficient to
put the pass device into a low impedance state between the first
terminal and the second terminal of the pass device.
9. The surge-tolerant power supply of claim 8, wherein the bias
circuit is configured to provide a voltage ramp at the output of
the bias circuit during a start-up period.
10. The surge-tolerant power supply of claim 8, wherein the input
circuit comprises a transient voltage suppressor having a first
terminal electrically connected to a first input terminal of the
input circuit and a second terminal electrically connected to a
second input terminal of the input circuit.
11. The surge-tolerant power supply of claim 8, wherein the input
circuit comprises a polarity protection circuit having a first
terminal electrically connected to the first input terminal of the
input circuit and a second terminal electrically connected to the
positive output of the input circuit.
12. The surge-tolerant power supply of claim 8, wherein the voltage
converter circuit includes a switch mode DC-to-DC converter having,
as an input, the input of the voltage converter circuit, a
transformer driver having an input electrically connected to an
output of the switch mode DC-to-DC converter, an isolation
transformer having a primary winding electrically connected to an
output of the transformer driver, and a rectifier-filter circuit
having an input electrically connected to a secondary winding of
the isolation transformer and having an output configured to
provide the output voltage.
13. The surge-tolerant power supply of claim 12, wherein the
transformer driver is configured to delay an output signal of the
transformer driver for a predetermined time during a start-up
period.
14. The surge-tolerant power supply of claim 12, wherein the
transformer driver includes an over-voltage detection circuit
configured to shut down an output signal of the transformer driver
when a voltage level at the positive output of the input circuit is
above a predetermined level.
15. The surge-tolerant power supply of claim 13, wherein the
transformer driver includes a programmable processor configured to
shut down an output signal of the transformer driver when the
voltage level at the positive output of the input circuit is above
a predetermined level.
16. A surge-tolerant power supply comprising: an input circuit
configured to receive a source of DC voltage; a pass device having
a first terminal electrically connected to an output of the input
circuit; a voltage converter circuit having an input and at least
one output, the input being electrically connected to a second
terminal of the pass device; and a bias circuit having a first
input electrically connected to a first of the least one output of
the voltage converter circuit, a second input electrically
connected to the output of the input circuit, and an output
electrically connected to a control terminal of the pass device,
wherein the bias circuit is configured to apply, after a
predetermined start-up period, a voltage on the control terminal of
the pass device sufficient to put the pass device into a low
impedance state between the first terminal and the second terminal
of the pass device.
17. The surge-tolerant power supply of claim 16, wherein the bias
circuit is further configured to provide a voltage ramp on the
control terminal of the pass device during the predetermined
start-up period.
18. The surge-tolerant power supply of claim 16, wherein the
voltage converter circuit has a second output configured to provide
an output voltage.
19. The surge-tolerant power supply of claim 16, wherein the input
circuit comprises a transient voltage suppressor having a first
terminal electrically connected to a first input terminal of the
input circuit and a second terminal electrically connected to a
second input terminal of the input circuit.
20. The surge-tolerant power supply of claim 16, wherein the
voltage converter circuit includes a switch mode DC-to-DC converter
having, as an input, the input of the voltage converter circuit, a
transformer driver having an input electrically connected to an
output of the switch mode DC-to-DC converter, and an isolation
transformer having a primary winding electrically connected to an
output of the transformer driver.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to a power supply for an
appliance, and more particularly to a surge-tolerant power supply
for providing operating power to appliances in a locomotive.
BACKGROUND
[0002] Electrical appliances for use in a railroad locomotive often
derive operating power from a battery through power distribution
lines. The power distribution lines, in this case the battery
circuit, may deliver high surge voltages to an appliance's power
input. International rail electronics standards require that
electrical appliances used in locomotives should be able to
withstand applications of energetic, high voltage surge pulses and
transients carried through the power distribution lines. In
addition, non-rail electronics may have similar requirements to
withstand surge and transient pulses. However, providing a power
supply for appliances having a fixed voltage input, that operates
normally within a wide range of voltages, and survives high energy
surges and transients is technically challenging. Additionally,
limiting inrush current into the electrical appliances upon initial
application of the power provides additional challenges.
Furthermore, appliances must limit emissions of high frequency
currents into the power distribution lines. This requirement
typically bears the moniker, "conducted emissions". Successful
conformance to this standardized requirement prevents consequent
emission of RF interference from the power distribution lines.
[0003] European Patent Number 1,720,239 (the '239 patent) provides
a DC/DC converter that comprises a switch-mode power supply with a
switching transistor, in particular a MOSFET transistor, which is
coupled between a DC voltage supply and a load, and a controlling
circuit with a controller, which delivers driving pulses for the
switching transistor, and a transformer between the controller and
the switching transistor. The controlling circuit further comprises
a primary circuit with a capacitor and a clamping circuit with a
capacitor. A main feature of the '239 patent is that the
controlling circuit further comprises a timing circuit, which
switches the switching transistor off after a certain on-time of
the controller. However, the '239 patent does not provide a power
supply for protecting electrical appliances from an exposure to a
wide voltage range, high voltage surge transients, and the
generation of conducted emissions without suffering unduly large
thermal loads.
SUMMARY OF THE DISCLOSURE
[0004] In one aspect of the present disclosure, a surge-tolerant
power supply system is provided. The surge-tolerant power supply
system includes an input circuit having a first input terminal and
a second input terminal configured to receive a source of DC
voltage. The surge-tolerant power supply system also includes an
N-channel MOSFET having a gate terminal, a source terminal, and a
drain terminal. The N-channel MOSFET has a characteristic threshold
voltage between the gate terminal and the source terminal, and also
has a drain terminal that is electrically connected to a positive
output of the input circuit. The surge-tolerant power supply system
also includes a switch mode DC-to-DC converter having an input
electrically connected to the source terminal of the N-channel
MOSFET and a negative output of the input circuit. The
surge-tolerant power supply system further includes a transformer
driver having an input electrically connected to an output of the
switch mode DC-to-DC converter. The surge-tolerant power supply
system also includes an isolation transformer having a primary
winding electrically connected to an output of the transformer
driver. The surge-tolerant power supply system further includes a
rectifier-filter circuit having an input electrically connected to
a secondary winding of the isolation transformer and having an
output configured to provide an output voltage. The surge-tolerant
power supply system includes a bias circuit having a first input
electrically connected to the positive output of the input circuit
and a second input electrically connected to the negative output of
the input circuit. The surge-tolerant power supply system also
includes a DC bias boost circuit having a first input electrically
connected to an auxiliary winding of the isolation transformer, a
second input electrically connected to an output of the bias
circuit, and an output electrically connected to the gate terminal
of the N-channel MOSFET. The DC bias boost circuit is configured to
apply a voltage at the gate terminal of the N-channel MOSFET that
exceeds the characteristic threshold voltage between the gate
terminal and the source terminal of the N-channel MOSFET.
[0005] In another aspect of the present disclosure, a
surge-tolerant power supply is provided. The surge-tolerant power
supply includes an input circuit configured to receive a source of
DC voltage and a pass device having a first terminal electrically
connected to a positive output of the input circuit. The
surge-tolerant power supply also includes a voltage converter
circuit having an input and at least two isolated outputs. The
input is electrically connected to a second terminal of the pass
device, and a first isolated output of the at least two isolated
outputs is configured to provide an output voltage. The
surge-tolerant power supply further includes a bias circuit having
a first input electrically connected to a second output of the at
least two isolated outputs of the voltage converter circuit, a
second input electrically connected to the positive output of the
input circuit, and an output electrically connected to a control
terminal of the pass device. The bias circuit is configured to
apply a voltage on a control terminal of the pass device sufficient
to put the pass device into a low impedance state between the first
terminal and the second terminal of the pass device.
[0006] In yet another aspect of the present disclosure, a
surge-tolerant power supply is provided. The surge-tolerant power
supply includes an input circuit configured to receive a source of
DC voltage, a pass device having a first terminal electrically
connected to an output of the input circuit, and a voltage
converter circuit having an input and at least one output, the
input being electrically connected to a second terminal of the pass
device. The surge-tolerant power supply further includes a bias
circuit having a first input electrically connected to a first of
the least one output of the voltage converter circuit, a second
input electrically connected to the output of the input circuit,
and an output electrically connected to a control terminal of the
pass device, wherein the bias circuit is configured to apply a
timed voltage on a control terminal of the pass device sufficient
to put the pass device into a low impedance state between the first
terminal and the second terminal of the pass device.
[0007] In yet another aspect of the present disclosure, an
apparatus for providing surge-tolerant power to an appliance is
provided. The apparatus includes an input circuit for receiving a
source of DC voltage and a pass device having a first terminal, a
control terminal and a second terminal. The apparatus also includes
a first means for providing an output voltage based on an input of
the pass device and a second means for applying a voltage to a
control terminal of the pass device based on the output voltage.
The voltage is sufficient to put the pass device into a low
impedance state between the first terminal and the second terminal
thereof.
[0008] Other features and aspects of this disclosure will be
apparent from the following description and the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a functional block diagram of a surge-tolerant
power supply for an appliance of the locomotive, according to one
or more embodiments of present disclosure;
[0010] FIG. 2 is a circuit diagram of an exemplary implementation
of a surge-tolerant power supply system, according to one or more
embodiments of the present disclosure;
[0011] FIG. 3 is a graphical representation of start-up voltage
waveforms from a soft-start circuit, according to one or more
embodiments of the present disclosure; and
[0012] FIG. 4 is a circuit diagram of the surge-tolerant power
supply of FIG. 1 at transient voltage input condition, according to
one or more embodiments of the present disclosure.
DETAILED DESCRIPTION
[0013] The description set forth below in connection with the
appended drawings is intended as a description of various
embodiments of the described subject matter and is not necessarily
intended to represent the only embodiment(s). In certain instances,
the description includes specific details for the purpose of
providing an understanding of the described subject matter.
However, it will be apparent to those skilled in the art that
embodiments may be practiced without these specific details. In
some instances, well-known structures and components may be shown
in block diagram form in order to avoid obscuring the concepts of
the described subject matter. Wherever possible, corresponding or
similar reference numbers will be used throughout the drawings to
refer to the same or corresponding parts.
[0014] Any reference in the specification to "one embodiment" or
"an embodiment" means that a particular feature, structure,
characteristic, operation, or function described in connection with
an embodiment is included in at least one embodiment. Thus, any
appearance of the phrases "in one embodiment" or "in an embodiment"
in the specification is not necessarily referring to the same
embodiment. Further, the particular features, structures,
characteristics, operations, or functions may be combined in any
suitable manner in one or more embodiments, and it is intended that
embodiments of the described subject matter can and do cover
modifications and variations of the described embodiments.
[0015] It must also be noted that, as used in the specification,
appended claims and abstract, the singular forms "a," "an," and
"the" include plural references unless the context clearly dictates
otherwise. That is, unless clearly specified otherwise, as used
herein the words "a" and "an" and the like carry the meaning of
"one or more". Additionally, it is to be understood that terms such
as "left," "right," "up," "down," "top," "bottom," "front," "rear,"
"side," "height," "length," "width," "upper," "lower," "interior,"
"exterior," "inner," "outer," and the like that may be used herein,
merely describe points of reference and do not necessarily limit
embodiments of the described subject matter to any particular
orientation or configuration. Furthermore, terms such as "first,"
"second," "third," etc. merely identify one of a number of
portions, components, points of reference, operations and/or
functions as described herein, and likewise do not necessarily
limit embodiments of the described subject matter to any particular
configuration or orientation.
[0016] Generally speaking, embodiments of the disclosed subject
matter provide a surge-tolerant switching power supply. The
surge-tolerant switching power supply may be used to provide
operating power to appliances on a locomotive. The surge-tolerant
switching power supply may incorporate a pass device and a bias
circuit. The bias circuit may provide a bias boost voltage to a
control terminal of the pass device. The bias boost voltage may be
sufficient to put the pass device into a low impedance state. An
input for the bias circuit originates from a transformer winding or
other coupled inductor within the power supply circuit. The bias
circuit also includes a soft-start to limit an inrush current
flowing to the appliance.
[0017] FIG. 1 is a functional block diagram of a surge-tolerant
power supply 100 according to one or more embodiments of the
present disclosure. The surge-tolerant power supply 100 of the
present disclosure may be used with an appliance of a locomotive
(not shown), for example. In one example, the locomotive may
include a power source, such as an engine (not shown), that
provides power to drive the train, so that the locomotive may pull
and/or push the cars of the train. The locomotive further includes
a source 102 of DC voltage for supplying power to the appliances in
the locomotive. In one embodiment, the source 102 is a battery. The
source 102 provides an input voltage `V.sub.IN` to the appliance.
The source 102 has a positive terminal 106 and a negative terminal
108. In order to prevent a transient surge of high voltage from the
source 102 to the appliance, the source 102 is connected to the
surge-tolerant power supply 100. The "surge-tolerant power supply
100" is hereinafter interchangeably referred to as `the
surge-tolerant power supply system 100` and `the apparatus for
providing surge-tolerant power 100`.
[0018] The surge-tolerant power supply 100 may include an input
circuit 110. The input circuit 110 may receive the input voltage
`V.sub.IN` from the source 102. The input circuit 110 includes a
first input terminal 112 connected to the positive terminal 106 of
the source 102. The input circuit 110 includes a second input
terminal 114 connected to the negative terminal 108 of the source
102. The first input terminal 112 and the second input terminal 114
receives the input voltage from the source 102. The input circuit
110 may further include a Transient Voltage Suppressor (TVS) 116.
The TVS 116 may include at least a first terminal 118 electrically
connected to the first input terminal 112 of the input circuit 110
and a second terminal 120 electrically connected to the second
input terminal 114 of the input circuit 110. The TVS 116 suppresses
a surge in the input voltage `V.sub.IN` as provided by the source
102. A constructional and functional aspect of the TVS 116 is
explained in detail with reference to FIG. 2. As illustrated, the
TVS 116 includes a first output terminal 122 and a second output
terminal 124.
[0019] The input circuit 110 may further include a polarity
protection circuit 126. The polarity protection circuit 126
includes an input terminal 128 and an output terminal 130. The
input terminals 128a and 128b of the polarity protection circuit
126 is connected to the output terminal 122 and 124 of the TVS 116
respectively. In one embodiment, the polarity protection circuit
126 may be a diode rectifier circuit. In other embodiments, the
polarity protection circuit 126 may include two diode rectifiers
(one in the positive circuit and one in the negative circuit. In
other embodiments, the polarity protection circuit 126 may include
a bridge rectifier (four diodes). The polarity protection circuit
126 rejects the input voltage `V.sub.IN` having reverse polarity.
The polarity protection circuit 126 may eliminates any damage to
the appliance that may occur due to the input voltage `V.sub.IN`
having reverse polarity. Further, the polarity protection circuit
126 may also reject negative polarity surge input voltages, or make
positive and negative surge voltages appear similar by means of
full-wave bridge rectification. The output terminal 130a of the
polarity protection circuit 126 is connected to a positive output
132 of the input circuit 110. The output terminal 130b of the
polarity protection circuit 126 is connected to a negative output
156 of the input circuit 110.
[0020] The positive output 132 of the input circuit 110 may be
connected to a pass device 134. In the illustrated embodiment, the
pass device 134 is an N-channel MOSFET. The pass device 134 is
hereinafter interchangeably referred to as "the N-channel MOSFET
`M1`. In another embodiment, the pass device 134 may be any other
device including, but not limited to, a bipolar junction
transistor. The pass device 134 includes a first terminal 136, a
second terminal 138, and a control terminal 140. The first terminal
136 of the pass device 134 is hereinafter interchangeably referred
to as "the drain terminal 136". The second terminal 138 of the pass
device 134 is hereinafter interchangeably referred to as "the
source terminal 138". The control terminal 140 of the pass device
134 is hereinafter interchangeably referred to as "the gate
terminal 140". Specifically, the positive output 132 of the input
circuit 110 is connected to the first terminal 136 of the pass
device 134.
[0021] The surge-tolerant power supply 100 may include a bias
circuit 142. The bias circuit 142 may include a soft start circuit
144 and a DC bias boost circuit 146. The positive output 132 of the
input circuit 110 may be connected to an input 150 of the bias
circuit 142 and the soft start circuit 144. The soft start circuit
144 may provide a voltage ramp to the control terminal 140 of the
pass device 134 during a start-up period of the power supply 100. A
voltage ramp may serve to limit an inrush current when power is
provided during start-up of the power supply 100. The DC bias boost
circuit 146 may not add a bias boost during start-up of the
surge-tolerant power supply 100. The bias circuit 142 may include a
first input 148 and a second input 150. The second input 150 of the
bias circuit 142 may be fed by the positive output 132 of the input
circuit 110. The second input 150 may be connected to the soft
start circuit 144. The first input 148 may be connected to the DC
bias boost circuit 146. The first input 148 may be fed by an
isolated output 168 of isolation transformer 152 of the
surge-tolerant power supply 100. The bias circuit 142 may include
an output 154 electrically connected to the control terminal 140 of
the pass device 134. The bias circuit 142 may provide a bias to the
control terminal 140 of the pass device 134. More specifically, the
bias circuit 142 may apply a voltage on the control terminal 140 of
the pass device 134. The voltage applied by the bias circuit 142
may, in some embodiments, be sufficient to put the pass device 134
into a low impedance state between the first terminal 136 and the
second terminal 138, thereby reducing power dissipation of the pass
device 134.
[0022] The surge-tolerant power supply 100 may further include a
bulk capacitor `C.sub.BULK` connected across the second terminal
138 of the pass device 134 and a negative output terminal 156 of
the input circuit 110. The bulk capacitor `C.sub.BULK` is charged
by a drain current `I.sub.D` flowing from the first terminal 136 to
the second terminal 138 of the pass device 134. The drain current
`I.sub.D` charges bulk capacitor `C.sub.BULK` based on the
following equation. The drain current `I.sub.D` required to charge
the bulk capacitor `C.sub.BULK` is:
I.sub.D=C.sub.BULK(dV/dt).
[0023] By controlling a voltage `V.sub.GS` at the control terminal
140 of the pass device 134, the pass device 134 may control the
drain current `I.sub.D` into the bulk capacitor `C.sub.BULK` of the
surge-tolerant power supply 100.
[0024] The surge-tolerant power supply 100 may further include an
electromagnetic compatibility (EMC) filter 158. The EMC filter 158
may be connected across the bulk capacitor `C.sub.BULK`. The EMC
filter 158 may filter high frequency signals to block them from
conducting into or conducting out of the input terminals 112 and
114. In one example, the high frequency signals may originate from
various components present at a later stage of the surge-tolerant
power supply 100. In another example, the high frequency signals
may originate from various electrical circuits disposed nearby to
the surge-tolerant power supply 100.
[0025] The surge-tolerant power supply 100 may also include a
Switch Mode Power Supply (SMPS) 160, which is well known in the
art. The SMPS 160 is hereinafter interchangeably referred to as
"switch mode DC-to-DC converter 160". The SMPS 160 may be
electrically connected, through EMC filter 158, to the bulk
capacitor `C.sub.BULK.` Once the bulk capacitor `C.sub.BULK` is
fully charged by the drain current `I.sub.D` of the pass device
134, the SMPS 160 starts its operation. The SMPS 160 converts the
input voltage `V.sub.IN` to a predetermined fixed DC voltage.
[0026] The SMPS 160 may be electrically connected to a transformer
driver 162. The input provided to the transformer driver 162 is a
DC voltage. The transformer driver 162 converts the DC voltage to
an AC voltage. That is, an output signal of the transformer driver
162 is the AC voltage. The transformer driver 162 may include a
circuit for delaying its output signal for a predetermined time
during a start-up period of the surge-tolerant power supply 100.
The transformer driver 162 may further include a circuit for
shutting down an output of the transformer driver 162. In one
embodiment, the circuit for shutting down the output of the
transformer driver 162 may be an over-voltage detection circuit
(not shown). The over-voltage detection circuit may detect a
voltage level at the positive output 132 of the input circuit 110.
Further, the over-voltage detection circuit may determine whether
the voltage level at the positive output 132 of the input circuit
110 is above a predetermined level. The predetermined level may be
based on a specification of the surge-tolerant power supply
100.
[0027] In another embodiment, the circuit for shutting down the
output of the transformer driver 162 may be a programmable
processor (not shown). The programmable processor may detect a
voltage level at the positive output 132 of the input circuit 110.
Further, the programmable processor circuit may determine whether
the voltage level at the positive output 132 of the input circuit
110 is above the predetermined level. The programmable processor
may shut down the output of the transformer driver 162 when the
voltage level at the positive output 132 of the input circuit 110
is above the predetermined level.
[0028] In yet another embodiment, the transformer driver 162 may
include an oscillator. The oscillator may convert the DC voltage
input of the transformer driver 162 to an AC voltage.
[0029] The transformer driver 162 may include an output connected
to isolation transformer 152. The isolation transformer 152 may
include at least a primary winding `L1`, a secondary winding `L2`
and an auxiliary winding `L3`. The isolation transformer 152 may
include an input 164, electrically connected to the primary winding
`L1` of the isolation transformer 152. The input 164 of the
isolation transformer 152 may be fed by the transformer driver 162.
The isolation transformer 152 may further include at least two
isolated outputs. In the illustrated embodiment, the isolation
transformer 152 includes a first isolated output 166 and a second
isolated output 168. The secondary winding `L2` is connected to the
first isolated output 166. The first isolated output 166 may be
connected to a rectifier-filter circuit 170. The rectifier-filter
circuit 170 my rectify and filter an output voltage generated at
the secondary winding `L2` of the isolation transformer 152. An
output of the rectifier-filter circuit 170 is an output voltage
`V.sub.OUT` of the surge-tolerant power supply 100. The output
voltage `V.sub.OUT` may be supplied to an appliance in order to
power the appliance.
[0030] The auxiliary winding `L3` of isolation transformer 152 is
connected to the second isolated output 168. The second isolated
output 168 may also be connected to the first input 148 of the bias
circuit 142. The auxiliary winding `L3` may provide an input to the
DC bias boost circuit 146. The input provided by the third winding
`L3` is rectified and filtered in the DC bias boost circuit 146 to
generate a bias boost voltage. In one example, the bias boost
voltage may be 4.5V. As mentioned earlier, the control terminal 140
of the pass device 134 may be fed by the bias circuit 142. This
bias boost voltage may elevate the voltage at the control terminal
140 of the pass device 134 to a voltage sufficient to drive the
pass device 134 into a low impedance state. When driven in this
manner, the voltage between the first terminal 136 and the second
terminal 138 of pass device 134 may have a value of a few
millivolts, and hence a significant current may flow from the first
terminal 136 to the second terminal 138 of the pass device 134 with
low power dissipation.
[0031] FIG. 2 illustrates a circuit diagram of one exemplary
implementation of the surge-tolerant power supply system 100. For
the sake of brevity, the aspects of the present disclosure which
are already explained in detail in the description of FIG. 1,
including the EMC filter 158, the switched mode DC to DC converter
160, the transformer driver 162, and the isolation transformer 152
have not been explained in detail with regard to the description of
FIG. 2. The surge-tolerant power supply system 100 is connected to
the source 102 of DC voltage. The input voltage `V.sub.IN` may
range, for example, from approximately 20VDC to approximately
93VDC, with voltages as high as 130VDC in extreme situations. In
some embodiments, a normal input voltage required for an appliance
may have different nominal values including, but not limited to,
12VDC, 24VDC, 48VDC, and 74VDC. The source 102 provides an input
voltage `V.sub.IN` to the surge-tolerant power supply system 100
which, in turn, provides power to the appliance. In order to
prevent an over-voltage condition or transient surge on the input
voltage `V.sub.IN` from the source 102 affecting the appliance, the
source 102 is connected to the surge-tolerant power supply system
100.
[0032] In the illustrated embodiment, the input circuit 110 of the
surge-tolerant power supply system 100 may receive the input
voltage `V.sub.IN` from the source 102. The TVS 116 may provide a
clamping voltage slightly above the maximum expected voltage of the
source 102. If the input voltage `V.sub.IN` is above the maximum
expected voltage of the source 102, the TVS 116 may clamp the input
voltage to a specified voltage level. In the illustrated embodiment
of FIG. 2, the TVS 116 of the input circuit 110 may be a transient
suppression diode connected across the source 102. The transient
suppression diode may have a normal working voltage tolerance up to
130V. In one example, the TVS 116 may be implemented as an
SMCJ130CA, manufactured by Littelfuse.RTM. and Fairchild.TM.. The
SMCJ130CA provides a maximum clamping voltage of 209V while
shunting a pulse surge current of 7.2 amperes. Hence, any input
voltage, of limited energy, above 209V may be clamped by the
SMCJ130CA. In another example, the TVS 116 may be implemented as,
but not limited to, a metal oxide varistor, gas discharge tubes,
etc.
[0033] The polarity protection circuit 126 of the input circuit 110
may include a diode `D1`. The diode `D1` may provide reverse
polarity protection by blocking accidental application of reversed
polarity power. The diode `D1` may also reject surge pulses with
negative polarity. The input terminal 128 of the polarity
protection circuit 126 is connected to the input circuit 110. The
output terminal 130 of the polarity protection circuit 126 is
connected to the positive output 132 of the input circuit 110.
[0034] The diode `D1` may be connected to the bias circuit 142. In
the illustrated embodiment, the bias circuit 142 includes the soft
start circuit 144 and the DC bias boost circuit 146. The positive
output 132 of the input circuit 110 is connected to the soft start
circuit 144. The bias circuit 142 includes a first input 148 and a
second input 150. The second input 150 of the bias circuit 142 is
fed by the positive output 132 of the input circuit 110. The soft
start circuit 144 provides a relatively slow ramp voltage during
start-up of the surge-tolerant power supply that passes through the
DC bias boost circuit 146. In the illustrated embodiment, the soft
start circuit 144 includes a current source 172 and a Resistor
Capacitor (RC) circuit 174. The current source 172 may have a
constant output current. In one example, the constant output
current is approximately 0.7 mA. The current source 172 includes
transistors `Q1` and `Q2`, along with resistors `R1` and `R2`. On
application of the input voltage `V.sub.IN`, the soft start circuit
144 drives the constant output current into the RC circuit 174
which is connected to the current source 172. The RC circuit 174
includes a capacitor `C1` connected in parallel with a resistor
`R3`. The constant output current from the current source 172 ramps
a voltage at the RC circuit 174 based on the output current value
and a value of the capacitor `C1` and resistor `R3`. `R3` may have
a relatively large resistance value so that it has only a minor
effect on the ramp voltage, but may provide a discharge path for
the charge stored on `C1`. This discharge path may allow the bias
circuit to track the input voltage `V.sub.IN`, when `V.sub.IN`
changes, for example, from a higher voltage value to a lesser
voltage value. The ramp in voltage may serve to limit the inrush
current when power is provided during start-up of the
surge-tolerant power supply. A Zener diode (or avalanche diode)
`D2` may be connected in parallel with the RC circuit 174 to limit
a base reference voltage for the gate terminal 140 of the N-channel
MOSFET `M1`.
[0035] An output voltage of the soft start circuit 144 may be
connected to the DC bias boost circuit 146. The DC bias boost
circuit 146 includes a diode bridge circuit having diodes `D3`,
`D4`, `D5` and `D6` connected at four arms of a bridge. In one
example, the first input 148 of the bias circuit 142 is connected
across diodes `D5` and `D6`. The diodes `D5` and `D6` are connected
in series with a resistor `R4`. The first input 148 of the bias
circuit 142 may be electrically connected to the second isolated
output 168 of the isolation transformer 152. During normal
operation, the AC voltage from the L3 output of isolation
transformer 152 may be rectified by the diode bridge in DC bias
boost circuit 146 and filtered by capacitor `C2`.
[0036] In the illustrated embodiment, an output of the DC bias
boost circuit 146 may be electrically connected to the N-channel
MOSFET `M1`. As mentioned earlier, the N-channel MOSFET `M1`
includes the drain terminal 136, the source terminal 138 and the
gate terminal 140. The N-channel MOSFET `M1` has a characteristic
threshold voltage `V.sub.T` between the gate terminal 140 and the
source terminal 138. The source terminal 138 and the gate terminal
140 may be interconnected with a diode D11. Further, the drain
terminal 136 may be electrically connected to the positive output
132 of the input circuit 110. The output of the DC bias boost
circuit 146 may be connected to the gate terminal 140 of the
N-channel MOSFET `M1`. During normal operation, the output of DC
bias boost circuit 146 may elevate a voltage at the gate terminal
140 of the N-channel MOSFET `M1` above the voltage at the source
terminal 138 by at least the characteristic threshold voltage
`V.sub.T` of the N-channel MOSFET `M1`, placing the N-channel
MOSFET `M1` in a low impedance state with little power
dissipation.
[0037] In the circuit illustrated in FIG. 2, the voltage between
the drain terminal 136 and the source terminal 138 (`V.sub.DS`) is
the sum of the voltage `V.sub.DG` between the drain terminal 136
and the gate terminal 140 and a voltage `V.sub.GS` between the gate
terminal 140 and the source terminal 138. In one example, during
start-up of the surge-tolerant power supply system 100, the voltage
between the gate terminal 140 and the source terminal 138
(`V.sub.GS`) ranges from 1V to 4.5V for the N-channel MOSFET `M1`
having relatively high transconductance. Hence, without the boost
voltage provided by DC bias boost circuit 146, the steady state
power dissipation of the N-channel MOSFET `M1` may be as high as
13.5 watts for an appliance having a 3 ampere current demand.
[0038] In one example, the bulk capacitor `C.sub.BULK` may be
connected to the source terminal 138 of the N-channel MOSFET.
During start-up of the surge-tolerant power supply 100, the drain
current `I.sub.D` from the N-channel MOSFET `M1` charges the bulk
capacitor `C.sub.BULK` with a straight line voltage
characteristic.
[0039] The surge-tolerant power supply 100 may include a
rectifier-filter circuit 170 connected to the secondary winding
`L2` associated with the first isolated output 166. The
rectifier-filter circuit 170 may rectify and filter an output
voltage generated at the secondary winding `L2` of the isolation
transformer 152. In one embodiment, the rectifier-filter circuit
170 may include a full wave rectifier circuit 176. The full wave
rectifier circuit 176 may include diodes D7, D8, D9, and D10. The
full wave rectifier circuit 176 converts an AC output voltage
generated by the isolation transformer 152 to DC output voltage. An
output of the full wave rectifier circuit 176 is connected to a
filter circuit 178 having a resistor R5 and capacitors C4 and C5.
The filter circuit 178 filters the ripples of the output of full
wave rectifier circuit 176. An output of the rectifier and the
filter circuit 178 is an output voltage `V.sub.OUT` of the surge
tolerant power supply system 100. The output voltage `V.sub.OUT`
may be supplied to the appliance to power the appliance.
[0040] In exemplary operation, when the N-channel MOSFET `M1`
charges the bulk capacitance `C.sub.BULK`, the switched mode DC to
DC converter 160 and the transformer driver 162 may operate to
drive the isolation transformer 152. The auxiliary winding `L3` of
the isolation transformer 152 provides an input AC voltage to the
first input 148 of the DC bias boost circuit 146. The DC bias boost
circuit 146 may rectify and filter the AC voltage to produce a DC
bias boost voltage. This may cause the voltage at the gate terminal
140 of the N-channel MOSFET to elevate above the voltage at the
source terminal 138 by at least the characteristic threshold
voltage `V.sub.T` of the N-channel MOSFET `M1`, placing the
N-channel MOSFET `M1` in a low impedance state with minimal power
dissipation.
[0041] FIG. 3 is a graphical representation 180 of a startup
voltage waveform of the soft start circuit 144 of the
surge-tolerant power supply 100. A first graphical representation
182 depicts the input voltage `V.sub.IN` supplied to the soft start
circuit 144 by the input circuit 110 for a time interval `T`. Based
on the input voltage, the current source 172 of the soft start
circuit 144 may generate a constant current of 0.7 mA. A second
graphical representation 184 depicts an output voltage of the soft
start circuit 144. Based on the constant input current, this ramps
the voltage across capacitor `C1` in a straight line with a slope
determined by the current value and the capacitance value
(V=I.DELTA.t/C). The soft start circuit 144 provides a maximum
output voltage `V.sub.C` across capacitor `C1` and the resistor
`R3` of the RC circuit 174 that is either `V.sub.IN` or the
Zener/avalanche voltage of diode `D2,` whichever is less. The
output voltage remains at the maximum output voltage `Vc` at the
time interval `T` until the input voltage `V.sub.IN` is removed.
Once the supply of input voltage `V.sub.IN` is removed, the output
voltage across the RC circuit 174 gradually decreases to zero.
[0042] FIG. 4 is a simplified circuit diagram illustrating an
operation of the surge-tolerant power supply 100 during a transient
event. When a transient input voltage appears at the source 102,
the TVS 116 of the surge-tolerant power supply 100 may clamp the
input voltage `V.sub.IN` to a voltage level acceptable for safe
operating conditions of the surge-tolerant power supply 100. The
TVS 116, in some embodiment, may provide a clamping voltage of
approximately 209V while shunting a pulse surge current of 7.2
amperes. Hence, transients of limited energy above 209V may be
clamped by the TVS 116.
[0043] In an exemplary transient event, a transient input voltage
appearing at the first terminal 136 of the pass device 134 may be a
low impedance voltage pulse of approximately 200V with duration of
about 500 microseconds. In such a scenario, the voltage at the
first terminal 136 may increase but the voltage at the second
terminal 138 may remain below the voltage at the control terminal
140, which may have an instantaneously fixed value. The pass device
134 may therefore block the 200V pulse from entering the EMC
filter, SMPS, and transformer driver (collectively illustrated as
190) by offering a high impedance to the circuit. A transient
voltage of much lesser magnitude may appear at the second terminal
138 of the pass device 134. An increase in the voltage at the
second terminal 138 may inject a substantial charge current into
the bulk capacitor `C.sub.BULK` further shunting the transient
input voltage from the protected circuitry.
INDUSTRIAL APPLICABILITY
[0044] The surge-tolerant power supply 100 provides substantial
over-voltage and surge immunity to protect an appliance from
exposure to a wide voltage range and high voltage surge transients
without suffering unduly large thermal loads. The surge-tolerant
power supply 100 has modest circuit complexity, high efficiency and
reduced thermal dissipation compared to typical high surge-tolerant
circuits.
[0045] While aspects of the present disclosure have been
particularly shown and described with reference to the embodiments
above, it will be understood by those skilled in the art that
various additional embodiments may be contemplated by the
modification of the disclosed machines, systems and methods without
departing from the spirit and scope of what is disclosed. Such
embodiments should be understood to fall within the scope of the
present disclosure as determined based upon the claims and any
equivalents thereof.
* * * * *